Physical materials generally change when they are subjected to an electric field, including electrostatic fields and those fields associated with electromagnetic waves. For example, an electric field can cause charge displacement within a material, thereby polarizing that material; the atoms or molecules of that material could be made to acquire induced dipole moments, and any molecules with permanent dipole moments could be realigned.
If an imposed electric field changes, the material will generally change, so as to track the change in the electric field to which it is subjected. For example, the charge displacement within a material will change in response to changes in an imposed electric field. Likewise, if an imposed magnetic field changes, the charge displacement within a material could change in response.
Thus, a material generally changes in the presence of an electric field, compared to the absence of an electric field, and it also changes when the nature of the imposed electric field changes.
In turn, an electric field is generally affected by the presence of a material as opposed to the absence of that material. Furthermore, when electrically significant change (for example charge displacement) occurs in that material, then the electric field is generally affected by that change in the material. The affected electric fields could include electrostatic fields and those fields associated with electromagnetic waves.
The change in the material generally lags temporally behind the change in the electric field. For example, the polarizing charge displacements in a material can move only at a finite speed, and cannot keep up with rapid changes in the imposed electric field.
The amount of temporal lag varies for different materials. For example, molecules with differing molecular weights, molecular shapes, and/or differing dipole moments, in materials at differing viscosities, (implying differing molecular arrangements) could respond with differing speeds and differing temporal lags to changes in the electric field.
There are several types of changes that can happen to a material in response to an imposed electric field, and several mechanisms that can produce such changes. For example, some types of polarization changes that can be caused in a material by an electric field are: electronic polarization, due to displacement of electronic charges; ionic polarization, due to displacement of ions; dipole polarization, due to reorientation of permanent dipoles; induced dipole moment polarization, due to distortion of the natural electrical distribution within a molecule or atom, even where such molecules are not permanent dipoles; and polarization by space charges, due to macroscopic displacement.
Each of these several types of changes involves a different mechanism, and thus a different type of temporal lag in the response of one given material. For example, it is known that space charge polarization could affect a material's dielectric constant most significantly at low frequencies of electric field change (power to audio); dipole polarization could affect a material most significantly at somewhat higher frequencies (audio to RF); ionic polarization could affect a material most significantly at yet higher frequencies (infrared to UV); and electronic polarization could affect a material most significantly at yet higher frequencies (UV to X-rays).
Since each of these mechanisms is frequency sensitive, and since different mechanisms become predominant at different frequencies, the response of any one material to an imposed changing electric field can vary significantly as a function of frequency. For example, the curve of the dielectric constant of a typical dielectric material varies dramatically as a function of frequency, due to the different polarization mechanisms becoming active, inactive, or even resonating at different frequencies. This dramatic variation in dielectric constant curve for a single material looks like a group of bandpass and resonant filters imposed on a frequency response curve, giving it a complex shape, which represents a signature pattern for that one material. The behavior of this material as a dielectric depends on its dielectric constant. Because the dielectric constant has a complex signature pattern as a function of frequency, this material will behave differently as a dielectric for different frequencies, in a complex signature pattern. Because time is simply the inverse of frequency, this material will also have a complex signature pattern of temporal behavior.
Thus, each material will generally have a signature pattern of response, in both the frequency and time domains, to an imposed changing electric field.
The temporal lag by the material in turn affects the electric field, altering the electric field. This alteration of the electric field, by a material subjected to that field, can have adverse consequences for some applications. For example, if a changing electric field represents a signal, then a temporally lagging change of that field by a material could corrupt that signal.
Furthermore, in those frequency regions where a material's response changes significantly as a function of frequency, this corrupting effect upon an electric field can be dispersive.
The signature pattern of temporally lagging response from each different material in turn can affect the electric field in a signature pattern manner, perhaps corrupting the electric field in a signature pattern. Thus, for example, one could examine the pattern of corruption of a signal represented by an electrical field, and, from the signature nature of this pattern of signal corruption, one might be able to ascertain precisely what material this electric field was imposed upon and in turn affected by.
If the material is employed as a dielectric in a capacitor, and if the electric field is an electrostatic field or a field associated with an electromagnetic wave, then the dielectric material can corrupt an electrical current, voltage, or signal being processed by the capacitor, and can do so in a signature pattern of corruption.
The signature pattern of corrupting temporal lags, from a dielectric material in a capacitor, could affect one frequency of change of the electric field differently than it affects another frequency. Thus, such a signature pattern of corruption would be especially damaging to a current, voltage, or signal that contained more than a single frequency. Any current, voltage, or signal that contains transients or more than one frequency could have its different frequencies corrupted to different extents by the signature pattern of corrupting temporal lags from the capacitor's dielectric. Thus, the signature pattern of corruption from the particular material of the dielectric could be especially noticeable and problematic on a current, voltage, or signal that contains more than one frequency, particularly where the differing plural frequencies span a range such that they are treated differently by the material's signature pattern. One such example is a current, voltage, or signal representing audio information, which often contains many frequencies at once, spanning several logarithmic decades, and where any foreign signature pattern of corruption is especially noticeable and problematic.
One material's signature pattern of corruption upon an electric field could be regarded as being similar to a small group of bandpass and resonant and anti-resonant filters, emphasizing some frequencies and suppressing other frequencies. One material generally might emphasize only a narrow band of frequencies, and suppress only a narrow band of frequencies. Thus, one material generally might have a strong coloration or personality that it imposes upon a signal represented by an electric field.
A second, different material could have a different signature pattern, similar to a different group of bandpass and resonant and anti-resonant filters operating at different frequencies from the first material.
When working with filters, it can sometimes be advantageous to spread out a single high Q resonance to become a low Q resonance over a wider span of frequencies, or a plurality of resonances covering a wider span of frequencies. The lower Q resonance or plurality of resonances affecting more frequencies imposes less coloration upon a signal than a high Q resonance affecting fewer frequencies. Indeed, in the limit, an infinite number of filter resonances affecting all frequencies could restore substantially flat response, resulting in substantially no coloration.
Likewise, when working with signature patterns of frequency emphasis and suppression by materials in an electric field, many resonances at many different frequencies could be advantageous over few resonances at few frequencies, by providing a less strongly colored signature pattern.
Thus, if a second different material has a signature pattern significantly different from a first material, then the combination of these two materials might provide less coloration of a signal than one material alone could provide.
Furthermore, the second material might be selected to be one having a signature pattern substantially complementary to the signature pattern of the first material in some aspects. For example, some of the frequencies emphasized by the first material could be suppressed by the second material. In such a case, the combination of these two materials might provide less coloration of a signal than one material alone could provide.
In addition, it could be further advantageous for the two different materials to be interspersed in some manner. If two materials are employed, but the first material is exclusively more proximate to a conductor (e.g. a capacitor plate) than the second material, then the signature pattern coloration of the first material might predominate, especially at certain high frequencies where the thickness of the more proximate first material could effectively place the more distant second material out of range. This could be disadvantageous in some applications. This problem could be solved by interspersing the two materials in some manner.